Sperm ultrastructure in two species of the polychaete genusHarmothoe (Polynoidae) |
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Authors: | M G Bentley Katrin Serries |
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Institution: | 1. Gatty Marine Laboratory, Department of Biology and Pre-clinical Medicine, University of St Andrews, KY16 8LB, Fife, Scotland, UK
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Abstract: | The structure of spermatozoa is described for two species of polynoid polychaete,Harmothoe imbricata andHarmothoe impar, from material fixed and examined by both scanning and transmission electron microscopy. The two species undergo spermiogenesis
within discrete testes. The testis ofH. imbricata is shown to have a layer of epithelial cells which possess an outer cuticular layer and a microvillous inner surface. Spermatocytes
of both species are spherical but there are marked differences in the shape and size of the spermatozoa of the two species.H. impar has a classical primitive spermatozoon with a rounded head (2 μm long) and a button-shaped acrosome. Fully differentiated
spermatozoa ofH. imbricata are modified from the primitive form by having a long head (10 μm length) with a pointed acrosome about 6 μm in length. Spermatozoa
ofH. imbricata have a ring of up to fourteen mitochondria around a centrally inserted flagellum at the posterior whereasH. impar has a ring of four or five spherical mitochondria. Spermiogenesis is well synchronised inH. imbricata but all developmental stages can be found simultaneously in the testis ofH. impar. The differences in sperm structure of the two species may be related to differences in breeding biology which are hitherto
unknown. |
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